<!DOCTYPE HTML>
<body>
<div style="position:fixed; left:0; top:0">
  <div style="position:absolute; z-index:2; left:0; top:0; width:100px; height:100px; background:red"></div>
</div>
<div style="position:absolute; z-index:1; left:0; top:0; width:100px; height:100px; background:lime"></div>
